1. Field of the Invention
The present invention relates to a field coil assembly of an electromagnetic clutch for a power transmission apparatus, and more particularly to a field coil assembly in which a lead wire of a coil for generating electromagnetic force in an electromagnetic clutch can be stably connected to a lead wire terminal of a connector for applying external power to the coil.
2. Description of the Prior Art
In general, an electromagnetic clutch for power transmission is an electric device for transferring driving force of a pulley rotated by an engine of a vehicle to a hub disc of a compressor driving shaft. If the electromagnetic clutch is powered on, a magnetic field is generated by electromagnetic induction of a winding coil, and the hub disc of the compressor driving shaft is attracted toward a frictional surface of the pulley by magnetic force due to the magnetic field, so that power of the engine is transmitted to a rotating shaft of the compressor. In addition, the electromagnetic clutch controls the operation of a cooling system of an air conditioning apparatus by regulating power of the compressor according to whether power is applied to the coil.
FIG. 1 is a perspective view illustrating the configuration of a field coil assembly of an electromagnetic clutch for a compressor according to the conventional art. As illustrated in FIG. 1, a bobbin 10 is installed at a core 1 forming a frame of the field coil assembly and includes a coil made of an aluminum (Al)-based material. The coil is obtained by repeatedly winding a wire and has a substantially ring shape, and both ends of the wire are drawn to form two lead wires W. The lead wires W are electrically connected to a lead wire terminal 26 of a connector 20 through bobbin terminals 15 of the bobbin 10 which will be described later.
The coil is surrounded by the bobbin 10. The bobbin 10 is provided at one side thereof with a coupling portion 11. The coupling portion 11 is a part at which the bobbin terminals 15 are installed and protrudes from one side of the bobbin 10 as illustrated in FIG. 1. The pair of lead wires W of the coil protrude through the coupling portion 11.
The bobbin terminals 15 are installed at the coupling portion 11. The bobbin terminals 15 are mounted on the coupling portion 11 to surround and fix the lead wires W. Furthermore, the bobbin terminals 15 are electrically connected to the lead wire terminal 26 of the connector 20 and thus electrically connect the coil to the connector 20. The bobbin terminal 15 is made of a copper (Cu)-based material. The lead wires W are connected to the bobbin terminals 15 by a soldering process.
The connector 20 is coupled to one side of the core 1 to transfer external power to the coil. The connector 20 includes a holder 22 coupled to the core 1, the lead wire terminal 26 coupled to the holder 22, and a clip 30 fixed to the holder 22.
The holder 22 is connected to the connector 20 and has a plate shape. The holder 22 is provided at the front end thereof with locking hooks 24 and on the upper surface thereof with connection portions 26′ of the lead wire terminal 26. The locking hook 24 corresponds to a locked hook 17 of the core 1, and is locked with the locked hook 17 to allow the connector 20 to be temporarily fixed to the core 1. The holder 22 is provided with a guide boss 28. The guide boss 28 guides the coupling of the clip 30 and extends vertically from the upper surface of the holder 22 as illustrated in FIG. 1.
The lead wire terminal 26 includes the connection portions 26′ and splicing portions 26″. The connection portions 26′ provided at one side of the lead wire terminal 26 substantially make contact with the bobbin terminals 15 and have a substantially plate shape as illustrated in FIG. 1. The splicing portions 26″ extending from the connection portions 26′ surround and fix cables W′ and simultaneously are electrically connected to the core wires of the cables W′. Meanwhile, the clip 30 is coupled to the holder 22. The clip 30 is coupled to the holder 22 while interposing the lead wire terminal 26 therebetween, thereby fixing the lead wire terminal 26.
However, the above-described conventional art has the following problems.
Since the melting point of the lead wires W of the coil is different from the melting point of the bobbin terminals 15, the lead wires W may not be firmly connected the bobbin terminals 15 at the time of soldering. Furthermore, since the bobbin terminals 15 and the lead wire terminal 26 are connected to each other only by the soldering process, a connection between the bobbin terminal 15 and the lead wire terminal 26 may be cut by impact such as vibration applied from an outside.